Simultaneous Enhancement of Thermoelectric and Mechanical Properties in Recyclable Transparent Ionogels via In-Situ Phase Separation

Wearable thermoelectric energy harvesting has garnered significant attention owing to its potential for powering flexible and self-sustaining devices. A major challenge in this field is the design of ionogels that balance mechanical strength with high ionic conductivity. Current ionogels often compromise one of these properties, which limits their practical use in flexible electronics. Addressing this gap is critical for the advancement of wearable thermoelectric technologies. Herein, we present an ionogel fabrication method that embeds hydroxypropyl cellulose (HPC) fibers into a biocompatible poly(vinyl alcohol) (PVA) matrix, which is then loaded with an ionic liquid (IL). This design significantly improved the mechanical properties of the ionogel by leveraging the reinforcing effect of the HPC fibers, which also created an IL-rich spherical structure through in situ microphase separation that promoted efficient ion migration. Ionogel-8515, which is the optimized formulation, exhibits superior performance, achieving an ionic conductivity of 36.79 mS cm^-1 and an ionic Seebeck coefficient of 2.783 mV K^-1, while maintaining excellent mechanical flexibility. Our results demonstrate that Ionogel-8515 not only meets the mechanical and conductive requirements for wearable applications but is also recyclable because of its reversible cross-linking network. This advancement bridges the current gap in ionogel design and offers a sustainable and efficient solution for future thermoelectric technologies.